142 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



SIlUii 



.503 



CONSIMILIS 



504 



S PAT U LATA 



505 



ALBICORNIS 



508 



GRANDIOSA 



509 A 



WAUBESIANA 



509 B 



Figs. 503-509. — Hydroptila larvae. 



7. Head varying from yellow with dark 

 marks arranged as in fig. SQ9A to much darker 

 with Hght areas as in fig. 5095; each notum 

 varies as shown: waubesiana. 



8. Head and pronotum almost entirely 

 black, head with at most an indistinct light 

 area between posterior and anterior dark 

 dorsal areas: probably dark specimens of ha- 

 mata. 



KEY TO SPECIES 

 Adults 



1. Apex of abdomen with complicated 

 set of appendages, figs. 510-526 



(males) 2 



Apex of abdomen tubular and with 

 simple parts, figs. 527-539 (females) 17 



2. Seventh sternite with a long median 



process either expanded at apex, 



straight or sinuate, fig. 515 3 



Seventh sternite with a short, spur- 

 like, median process, fig. 520 9 



3. Tenth tergite with apex divided into 



a pair of long, stout, heavily sclero- 

 tized arms curved sharply mesad at 



apex, fig. 510 xella, p. 148 



Tenth tergite divided only into semi- 

 membranous lobes 4 



4. Eighth sternite with an apico-mesal, 



heavily sclerotized projection; med- 

 ian process of seventh sternite sin- 

 uate and suddenly narrowed at apex, 



fig. 511 virgata, p. 148 



Eighth sternite without a mesal pro- 

 jection; median process of seventh 

 sternite expanded and flanged at 

 apex, or of even thickness, figs. 512, 

 515 5 



5. Claspers short and beaklike, tenth 



tergite projecting beyond them, fig. 



513 6 



Claspers long and slender, as long as 

 tenth tergite, figs. 514-516 7 



6. Aedeagus with apex divided into a 



pair of very slender rods, one 

 straight and the other sharply right- 

 angled close to end, fig. 512 



hamata, p. 149 



Aedeagus without one apical rod so 

 sharply angled, at most as in fig. 

 513 amoena, p. 150 



7. Apex of aedeagus with a definite knob 



beyond lateral spur near tip, fig. 514 



spatulata, p. 148 



Apex of aedeagus with lateral spur at 

 tip, figs. 515, 516 8 



8. Tenth tergite with apex blunt and un- 



expanded, fig. 515 vala, p. 148 



Tenth tergite with apex divided into 

 a pair of laterally directed, sharp 

 points, fig. 516 armata, p. 147 



9. Tenth tergite with apex divided into a 



pair of hornlike spikes directed 

 laterad, fig. 517. . . .waubesiana, p. 150 

 Tenth tergite without such apical 

 structures, fig. 518 10 



10. Tenth tergite with apex divided into a 



pair of lateral, slender, sinuate fila- 

 ments curved under the apico-dorsal 

 projections of the claspers, fig. 518 



delineata, p. 151 



Tenth tergite without such apical 

 structures, figs. 519-525 11 



11. Eighth sternite with a row of 4 to 6 



stout black spines at each apico- 

 dorsal corner, fig. 519 



grandiosa, p. 151 



Eighth sternite without stout black 

 spines 12 



